The present invention relates to nuts, and particularly to an improved process for preparing defatted nuts.
The term "nuts" as used in this description includes whole nuts and pieces of nuts such as peanuts, almonds, Brazil nuts, filberts, pecans, walnuts, and the like. For purposes of conciseness in description, the following disclosure will center around the production of low-fat peanuts. It is not intended, however, to be limited to peanuts because the principles which will apply for peanuts should apply to other nuts.
The basic procedures for preparing partially-defatted nuts have been known for a number of years. For example, in U.S. Pat. No. 2,003,415 to Ammann and U.S. Pat. No. 3,294,549 to Vix et al, there are described procedures for pressing the oil from nuts such as peanuts. Broadly, these methods include the steps of pressing nuts until the desired quantity of oil is removed, and then steaming or cooking the partially-defatted nuts in water until the nuts are reconstituted to substantially their original size and shape. Both of these patents discuss the virtues of partially defatted nuts in the diet.
In U.S. Pat. No. 3,294,549, Vix et al indicate that the resulting high protein products have excellent flavor, aroma, taste, texture, and appearance, and good shelf life. They indicate that their process can be performed on raw, toasted, blanched or unblanched nuts with equivalent results; however, no example is directed to toasted nuts and there is no teaching or suggestion that pretoasted nuts, when properly processed, will be more flavorful. One series of Examples discusses hot pressing wherein the nuts are steamed or otherwise moistened and then further heated to a temperature (104.degree. C.) less than required for roasting for flavor development; thus, there was no disclosure that this alternate process improved final product flavor or texture. Moreover, this hot pressing technique resulted in 32.8% of the product being broken to the extent that it passed through a four-mesh screen. This hot pressing technique is similar to that of Ammann who disclosed heating to a temperature of 80.degree. to 90.degree. C. prior to pressing. Further work on the Vix et al process is described in a series of articles entitled "Development and Potential of Partially Defatted Peanuts," Peanut Journal and Nut World, January and February 1967, and an article entitled "Low Calorie Peanuts", Food Processing/Marketing, September, 1965.
Later workers, encouraged by the apparent appeal of products of that type to weight conscious consumers, continued to work in this area. Because the caloric density of fat is twice that of protein and carbohydrates, the removal of such a significant amount of fat from nut products could result in significant calorie reduction. Moreover, because these products were typically less dense than the normally treated non-defatted nuts, yet further calorie reductions were obtainable. In U.S. Pat. No. 3,645,752 to Baxley, there is disclosed a process which is said to improve the flavor of partially-defatted nuts by quenching them in a flavored oil after roasting. In U.S. Pat. No. 3,740,236, also to Baxley, it is indicated that the roasted peanut flavor appears to be reduced in proportion to the percentage of the peanut oil removed during the pressing process. Baxley, however, does not directly confront this flavor loss but provides a process for improving flavor of the nuts once the flavor is diminished. According to this patent, the defatted nuts are reconstituted in an aqueous binder solution which can also contain flavors.
Gannis et al, in U.S. Pat. No. 4,049,833, also recognized the adverse effect on the flavor and texture of partially-defatted nuts. To correct this, Gannis et al suggested contacting the partially-defatted nuts with a glycerol-containing solution during reconstitution, prior to roasting. They disclosed that after roasting, the treated nuts have improved flavor, texture and storage stability.
The exact reason for the flavor loss in the partially-defatted nuts is not fully understood. The Doctoral Dissertation of M. E. Mason entitled Procedures in Studying and Factors Influencing the Quality and Flavor of Roasted Peanuts, Oklahoma State University, 1963, pages 63 and 64, indicates that oil pressed from peanuts contain aleurone grains, among other particulates, which appear to contain flavor precursors. The Mason dissertation, however, was not concerned with the preparation of low-fat nuts, but simply gaining a better knowledge of the source and identification of flavor principals in peanuts.
U.S. Pat. No. 4,329,375 to Holloway and Wilkins discloses a process for preparing low-fat nuts, such as peanuts which retain more of their natural flavor and texture than products prepared by earlier prior art procedures. They disclosed that they had found several factors important to achieving a high quality product. Among these were pre-roasting the nuts to partially develop a roasted nut flavor and color, pressing only after equilibration of the internal nut moisture, and limiting the amount of oil extraction. Products prepared according to the process have achieved commercial success; however, the processing time and equipment necessary to achieve moisture equilibration is more costly than would be desired and, while the process results in the production of more acceptable (whole or half, but unbroken) nuts than the prior art, improved yields are still desired.